Administration frequency as well as dosage of PTH are associated with development of cortical porosity in ovariectomized rats

The effect on bone porosity of a drug that promotes bone growth depends on the dosing and treatment frequency. A team in Japan led by Tadahiro Iimura from Ehime University and Ryoko Takao-Kawabata from Asahi Kasei Pharma Corporation injected female rats that had had their ovaries removed to mimic the effects of menopause with 15 different regimens of a synthetic form of the human parathyroid hormone. The regimens comprised four different concentrations of the drug and four distinct administration frequencies. The researchers found that more frequent treatment schedules and higher hormone doses created more porous, fragile vertebrae that were prone to fractures. These changes in bone microarchitecture were more pronounced in the front part of the vertebrae than in the back. The findings could help inform clinical dosing regimens for post-menopausal women receiving synthetic parathyroid hormone.